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69 Cards in this Set
- Front
- Back
Ig alfa Ig beta |
invariant molecules whose function is to deliver to the inside of the B-cell the activation signals that are triggered by membrane Ig |
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BCR complex |
membrane IgD or IgM+Ig alfa or Ig beta on B cells |
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TCR |
membrane-bound molecule found on T cells to recognize MHCs. Comparable to Ig on B cells. They transmit the signal inside the cell thanks to CD3 and ζ-chains. |
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cross-linking |
activation of B cells by epitopes |
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antibodies |
Igs: composed of 2 heavy chain and 2 light chains |
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Fab region |
fragment antigen binding, to be found on antibodies |
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Fc region |
tail region of an antibody that interacts with cell surface receptors called Fc receptors and some proteins of the complement system (fragment crystallizable region) |
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heavy isotype switching |
=switching in isotype of heavy chain in the antibodies. It happens to T-dependent B cells after been activated by CD4+ lymphocytes together with the process of affinity maturation, B cells proliferation (clonal expansion) and production of Igs |
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IgD |
naive B cell antigen receptor |
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IgM |
pentamer -naive B cell antigen receptor -complement activation |
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IgA |
<-cytokines produced in mucosa (a.o. TGF beta) -mucosa immunity |
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IgG |
<-IFN gamma
-neonatal immunity -antibody feedback mechanism -ADCC -macrophages activation through Fc gamma |
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IgE
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<-IL-4 -helmithic infections -mast cells activation (fc epsilon)-hypersensitivity -allergy |
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CD3 and ζ-chains |
They transmit the signal from TCR into the T cells |
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TCR complex |
TCR+ CD3 and ζ-chains |
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somatic gene recombination |
V(D)J recombination is the mechanism of genetic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. The process results in the highly diverse repertoire of antibodies/immunoglobulins (Igs) and T cell receptors (TCRs) found on B cells and T cells, respectively |
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CD4 and CD8 |
co-receptors on T cells to recognize II MHC and I MHC, respectively |
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what is needed for antigen recognition on T helper cells? |
-TCR - CD3 and ζ-chains -co-receptors CD4 or CD8 -adhesion molecules (integrins) -costimulator (CD28+B7) |
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CD28-B7 interaction |
B7=proteins expressed on APCs as costimulators of T cells CD28= receptor present on all T cells to recognize B7 |
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CD40 Ligand |
-present on T cells, activates macrophages, B cells and B7 costimulators for T cells |
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CD40 |
-present on APCs, when it binds with CD40L on T cells it stimulates expression of B7 costimulators and cytokines -present on macrophages->activation by T cells -present on B cells->production of antibodies |
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immunologic synapse |
region of contact between APC and T cell |
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ITAMs |
=immunoreceptors tyrosine-based activation motifs -present on CD3 and ζ-chains of T cells -prensent on Ig alfa and beta of B cells when phosphorylated it triggers effector pathways inside the lymphocyte->recruitment of adapter proteins-> activation of biochemical intermediates-> transcription factors (a.o. NF-kB)-> cytokines productions, cytokines receptors expression, effector molecules (CD40L) |
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Functional responses of T cells |
1. Cytokines secretion 2. Clonal expansion 3. Differentiation into effector cells 4. Memory 5. Negative feedback |
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Cytokines properties |
-produced in response to antigen -autocrine or paracrine -pleiotropism: multiple actions -redundancy: several cytokines have the same action |
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IL-2 |
<-CD4+ and CD8+ -> T cells growth and differentiation factor |
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IL-4 |
<- CD4+ (Th2) -> switching to IgE ->Th2 |
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IL-5 |
<-CD4+ (Th2) -> activation of eosinophils |
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IFN-gamma |
<-CD4+, CD8+ and NK -> activation of macrophages ->Th1 ->IgG switching much more |
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IL-12 |
<-macrophages ->NK activation ->Th1 |
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TGF-beta |
<- CD4+, macrophages, others -/ inhibition T cells, B cells and macrophages |
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Th1 |
<- IFN gamma, IL-12 -> IFN gamma-> macrophages (CD40L) ->IL-2 -> T cells, NK cells, B cells proliferation ->TNF |
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Th2 |
<-IL-4 ->IL-4-> IgE switching ->IL-5-> eosinophils ->IL-13 ->alternative macrophages activation for tissue repair |
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Th17
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<-IL-1, IL-6, TGF beta ->IL-17 ->IL-22 =barrier function, neutrophils attraction, against bacteria and fungi |
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IFN gamma |
<-NK, Th1, CD8+
-> macrophages activation -> Th1 differentiation much more |
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I MHC |
diplayed by all nucleated cells
recognized by CD8+ |
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II MHC |
displayed by APCs recognized by CD4+ |
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Granzymes |
granule proteins produced by CD8+, they cleave and thereby activate enzyme caspase to induce apoptosis in an infected cell |
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Perforin |
granule proteins produced by CD8+, responsable for the delivery of granzymes inside the infected cell |
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T dependent B cells charateristics (=follicular B cells) |
-heavy isotope switching -affinity maturation -long living plasma cells |
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T indipendent B cells |
marginal zone B cells (in splenic white pulp for blood-borne polysaccharides) B-1 cells (in mucosa for nonprotein antigens) |
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Time of primary response |
5-10 days |
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Time of secondary response |
1-3 days |
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What is the second signal for B cells? |
C3d complement fragment (also microbial products on TLRs), that enhance the activation together with signal 1 (the antigen) attached to membrane Igs |
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Consequences of B cell activation |
1. B cell proliferation 2. B cell differentiation 3. production of IgM (first humoral response) 4. migration out of follicle 5. B cell present II MHC to T cell |
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What does the T cell express to activate the B cell? |
CD40L |
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trigger of antibody feedback |
IgG |
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Effects of antibodies (4) |
1. Neutralization of microbe and toxins 2. Opsonization and phagocytosis (IgG+phagocytes) 3. ADCC (IgG+NK) 4. Complement activation |
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Effects of complement activation (3) |
1. Lysis of microbes 2. Phagocytosis of opsonized microbes 3. Inflammation |
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Poly-Ig receptor |
receptor present on the basal side of the epithelium that binds to IgA and bring it to the lumen where it is cleaved off by a proteolitic enzyme |
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cross-presentation |
the ability of certain antigen-presenting cells to take up, process and present extracellular antigens with MHC class I molecules to CD8 T cells |
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PAMPs |
Pathogen associated molecular patterns, recognized by PRRs |
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PRRS |
Patter recognition receptors |
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NF-kB and IRF-3 |
transcription factors activated by TLRs |
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TNF |
Tumor necrotic factor, proinflammatory cytokine produced by macrophages and Th1 |
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IL-1 |
proinflammatory cytokine produced by macrophages and endothelial cells |
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IL-12 |
cytokines produced by macrophages that activates NK |
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E-selectin, P-selectin |
low affinity molecules expressed on epithelial cells to attach selectin ligands on leukocytes->rolling |
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Integrins |
high affinity molecules present on leukocytes that attach for instance ICAM-1 |
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Metabolic effects of proinflammatory cytokines |
Endothelial cells: activation Phagocytes: activation Hypothalamus: fever Liver: synthesis of acute phase proteins (a.o. CRP) Muscle, fat: catabolism |
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Follicular dendritic cells |
APCs for B cells |
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NK-T cells |
they recognize lipids ipv peptides antigens (probably) |
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GammadelyaT cell |
they recognize different types of antigens displayed, not only peptides |
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DM |
proteinthat remove the CLIP from IIMHC from ER |
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CLIP |
invariant chain attached to IIMHC in ER, removed by DM |
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Immunodominant epitopes |
the only peptide of an antigen thatstimulate immune response (after been broken down) |
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TAP |
protein, transportassociated with antigen processing from cytoplasamtic proteasome to ER withIMHC |
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Functions of the complement |
1. MAC complex lysis of microbe 2. C3b coats microbe for phagocytosis 3. C3d activates humoral response 4. C5a,C4a, C3a proinflammatory |
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3 pathways of complement actiavtion |
1. Alternative (directly bound to antigen) 2. Classical (IgM or IgG) 3. Lectin (mannone binding lectin) |